[mythtv-users] Re: Capture card with best tuner - BT8x8, SA713x or PVR-250?

[Jarod C. Wilson]

On Thursday, Joe Votour wrote:

> An update on the continuing saga...
>
> I decided to try to figure out whether it was the
> backend or the frontend causing the problems, so I did
> a recording only at 352x480.  The playback of the
> resulting video was jerky in both MythTV and mplayer
> (with the nuv patch installed) in the same places.
> Thus, I'm concluding that mythbackend is the culprit.
>
> I then installed MythTV 0.11 on my Pentium 4, 2.4GHz,
> 512MB RAM, using the same capture card (Pinnacle
> PCTV), and still had the same problems with
> rebuffering messages an dropped frames.
>
> At that point, I decided to splurge and get a PVR-250
> card, just to see how it helps things (I put it in the
> Athlon XP+ 2400 system I'm using for MythTV).  I can't
> capture at 720x480 or 544x480 (still getting
> stuttering/pausing, but very rarely) not even 480x480
> works (though this might be the "ghosting" issue that
> is known about).  Maybe 480x480 isn't a correct
> resolution for the PVR-250?

That isn't the ghosting issue, and 480x480 is a valid resolution for 
the PVR-250.

> I'm guessing that the "rebuffering" message comes up
> only during software enoding (from a bt8x8 card, for
> instance), since when I got the pausing with the
> PVR-250, there was nothing on the console where
> mythbackend was running.

I believe you are correct on that one.

> So, given this, I can only consider that it's one of
> four things:
> 1. Red Hat 9 is broken, even with a kernel upgrade to
> 2.4.22.

I assure you Red Hat Linux 9 is not broken. I would have suspected a 
tanked install as a possibility on the first install, but since you 
have the problem on the second machine also, I think your install is 
fine. I've done the install a good 10-20x on RHL9, and it always works.

> 2. MythTV is somehow broken.

I think not. Works beautifully on RHL9 here.

> 3. DMA is broken with Western Digital hard drives (and
> the kernel and hdparm lie about it).  All of the hard
> drives I'm using are WD's (I used a 60GB model, a
> 100GB model and a 120GB model, all 7200RPM, 2MB
> buffer).  Unfortunately, the only hard drives I have
> kicking around here are WD.

No, Western Digital drives are some of the best supported. I have quite 
a few of them around here myself. DMA definitely isn't broken, unless 
your motherboard is the culprit (not likely, since you have the problem 
on two different systems).

> 4. The signal from my cable provider really is to
> blame.  Unfortunately, this may not be fixable (need
> to talk to the landlord to see if they've looked into
> it).

Of the four options you suggest, this is the most likely. Probably too 
much attenuation and signal loss on the line. At one point, I was 
running a splitter and a rather long cable to my test system, and the 
signal got bad enough that I saw pauses like you describe. Moving the 
test system to a location where there was no splitter, and eliminating 
an excess of about 35ft of cable cleaned the signal up right away, and 
the pauses were gone. Try to eliminate as much cabling as possible. If 
that fails, you might look into a signal booster.

> I will say that the picture from the PVR-250 is
> clearer than that which I got from my Pinnacle card,
> but for $150, I want more than a pretty picture - I
> want a pretty picture that doesn't skip.

Yeah, the PVR-250 has a far superior picture to most low-end cards...

> I guess we'll see what happens while I watch Live TV
> tonight.

Probably more of the same... :-(

--Jarod

-- 
Jarod C. Wilson, RHCE

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MythTV, Red Hat Linux 9 & ATrpms documentation:
http://pvrhw.goldfish.org/tiki-page.php?pageName=rh9pvr250